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For more information and examples, see Section 9.1.8 "Id Annotation" of the [http://jcp.org/en/jsr/detail?id=220 JPA Specification].
 
For more information and examples, see Section 9.1.8 "Id Annotation" of the [http://jcp.org/en/jsr/detail?id=220 JPA Specification].
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Revision as of 12:27, 15 June 2010

@Id

Use the @Id annotation to designate one or more persistent fields or properties as the entity's primary key.

For each entity, you must designate at least one of the following:


Note: The last option in the preceding list – @Id and @IdClass combination – is applicable to composite primary key configuration.


The @Id annotation does not have attributes.

By default, EclipseLink persistence provider chooses the most appropriate primary key generator (see @GeneratedValue) and is responsible for managing primary key values: you do not need to take any further action if you are satisfied with the persistence provider's default key generation mechanism.

This example shows how to use this annotation to designate the persistent field empID as the primary key of the Employee table.

Usage of @Id Annotation

 @Entity
 public class Employee implements Serializable {
     @Id
     private int empID;
     ...
 }

The @Id annotation supports the use of EclipseLink converters (see Using EclipseLink JPA Converters).

For more information and examples, see Section 9.1.8 "Id Annotation" of the JPA Specification.


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